Load custom ACPI tables

custom_acpi_tables.md

ACPI DSDT/SSDT patching

These instructions are meant for a system with EFI, systemd-boot and deb based packages. Adjust them to your needs.

Reference: https://www.kernel.org/doc/Documentation/acpi/initrd_table_override.txt

See also https://github.com/lbschenkel/acer-sf314_43-acpi-patch

ACPICA tools: https://acpica.org/downloads

sudo apt install acpica-tools

Option 1: DSDT, extract and modify the tables

Extract the acpi tables

mkdir acpi && cd acpi
sudo acpidump -b

Disassemble the tables

iasl -d dsdt.dat

Modify or patch the tables

vim dsdt.dsl

Assemble the custom tables

iasl -sa dsdt.dsl

Generate the cpio file for initrd

cd ..
mkdir -p kernel/firmware/acpi
cp acpi/dsdt.aml kernel/firmware/acpi/
find kernel | cpio -H newc --create > patched_acpi_tables.cpio

Grub does not require a cpio file, you can directly provide the dsl file.

Option 2: SSDT, create the tables

SSDT tables add missing features to the existing ACPI, without requiring disassembling. They are created using the same tools and procedure.

Assemble the custom tables

iasl -sa ssdt.dsl

Generate the cpio file for initrd

cd ..
mkdir -p kernel/firmware/acpi
cp acpi/ssdt.aml kernel/firmware/acpi/
find kernel | cpio -H newc --create > patched_acpi_tables.cpio

Install the tables (systemd-boot)

Copy the cpio file with the custom tables where it can be addressed by the EFI boot

sudo mkdir /boot/efi/EFI/acpi
sudo cp patched_acpi_tables.cpio /boot/efi/EFI/acpi/

Edit the entry sudo vim /boot/efi/loader/entries/Pop_OS-current.conf

linux /EFI/...
initrd /EFI/acpi/patched_acpi_tables.cpio
initrd /EFI/Pop_OS-.../initrd.img
options ...

@sieskei

Find your distro's grub config script in /ect/grub.d, I use Manjaro and the script related to adding boot options was 10_linux. There I found a series of complex process to detect kernels and add relevant boot options.
A block of code there was

  initrd=
  if test -n "${initrd_early}" || test -n "${initrd_real}"; then
    initrd="${initrd_early} ${initrd_real}"

    initrd_display=
    for i in ${initrd}; do
      initrd_display="${initrd_display} ${dirname}/${i}"
    done
    gettext_printf "Found initrd image: %s\n" "$(echo $initrd_display)" >&2
  fi

My poor understanding to shell scripting is enough to recognize that part is responsible for adding the initrd command. Since it first only adds the file name and later adds the /boot/ prefix, I changed the third line to:

initrd="${initrd_early} patched_dsdt.cpio ${initrd_real}"

So after running grub update command it correctly added the /boot/patched_dsdt.cpio between the Intel ucode and kernel initrd images.

This is likely not a great solution, though. The better way is to write your own script there to parch the options, and give it a larger prefix so it runs after the original boot options adding scripts.

Hello @fermino, @Moooebie
thank you for your assistance.

In the end, I managed to do it very easily by edit /etc/default/grub.
I added GRUB_EARLY_INITRD_LINUX_CUSTOM = "patched_acpi_tables.cpio" and move file to /boot.

To use it with grub, it is enough to copy acpi/dsdtl.aml to /boot/. Then I used a slightly modified version of this script to generate the grub configuration (https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1045690).

$ diff /boot/grub/grub.cfg.old /boot/grub/grub.cfg
88a89,95
> ### BEGIN /etc/grub.d/01_acpi ###
>  insmod part_gpt
>  insmod fat
>  search --no-floppy --fs-uuid --set=root 9FCD-44E3
> acpi ($root)/dsdt.aml
> ### END /etc/grub.d/01_acpi ###
> 

@fermino I have the same CSC3551 issue coming with my ASUS ROG Zephyrus G14 GA402XV as this one, and your way of applying a SSDT patch did make Linux correctly detect the woofer speakers. Unfortunately, after that, due to some unknown reason, the laptop started becoming hot and noisy even when idling. The battery started to drain very quickly after being unplugged, and battery life dropped from ~10hrs to 2-3hrs. Even when the laptop was under sleep the battery continued draining.

After some attempts it looks like this way of patching is indeed the culprit. The correct way instead is to copy the cpio file to /boot and add this file in the initrd line, such like this:
initrd /patched_acpi_tables.cpio /initramfs-linux.img
Now the battery life goes back to normal while the woofer speakers are still detected and working.

Anyone having done this patch notice that when the system volume is low the sound is more bass than treble and the reverse when the volume is high? Somewhere around 75% sounds pretty good. Wondering if it's just an issue on my end.

Let's go. My sound works perfectly.
For NixOS people, I made a module that is very easy to integrate into your NixOS configuration :
https://github.com/mrnossiom/dotfiles/blob/nixos/modules/nixos/asus-zenbook-ux3402za-sound.nix

Let's go. My sound works perfectly. For NixOS people, I made a module that is very easy to integrate into your NixOS configuration : https://github.com/mrnossiom/dotfiles/blob/nixos/modules/nixos/asus-zenbook-ux3402za-sound.nix

THANK YOU! I couldn't figure out how to nixify the instructions to work with systemd-boot, but your config just worked!